Oxidation-resistant oleaginous materials



United States Patent 01 OXIDATION-RESISTANT OLEAGINOUS MATERIALS Warren C. Ellis, Jr., Columbus, Ohio, assignor, by mesne assignments, to Staulfer Chemical Company, New York, N. Y., a corporation of Delaware No Drawing. Application December 14, 1954, Serial No. 475,309

18 Claims. (Cl. zeta-498.5

This invention relates to a method of stabilizing oleaginous materials such as fats, fatty acids and hydrocarbons and to such compounds containing small amounts of stabilizing agents as novel compositions of matter.

As is well-known, oleaginous materials absorb oxygen upon standing for any length of time and become dark and foul smelling. Many attempts have been made in the past to provide antioxidants which will render such materials resistant to oxidation for extended periods of time and at elevated temperatures but ordinarily such agents as have been proposed in the past are not fully effective and must be used in relatively large quantities.

According to the present invention, it has been found that rhodanines, including rhodanine itself and various substituted rhodanines, are very effective as antioxidants for oleaginous materials. At the relatively low concentration of 0.025% by weight, rhodanine renders commercial stearic acid virtually oxidation-proof. Although the substituted rhodanines are not as effective as rhodanine itself, these compounds do possess definite antioxidant properties and in some applications may even be preferred to rhodanine. By using rhodanine as an antioxidant, fatty acids such as commercial stearic acid (a mixture of stearic and palmitic acids) may be kept from develop ing rancidity and/or peroxides for practically any length of time desired, regardless of whether the fatty acids are maintained in the solid or liquid state, or in the presence or absence of air. Similarly, the rhodanines can be used to stabilize fats, such as lard oil and hydrocarbons such as paraffin wax.

Although rhodanine by itself is very effective, in some situations it has been found that rhodanine may be advantageously combined with other antioxidants to pro duce e en superior results.

ice

The rhodanines of the present invention possess the following structural formula:

R1N-C=0 3H1 s in In the above formula, R1 and R2 may be hydrogen atoms, in which case the compound is rhodanine itself, or R1 and R2 can be various organic substituents such as alkyl, aryl, alkaryl, aralkyl, or heterocyclic radicals. However, in carrying out the present invention, rhodanine itself is preferred because of its relatively low cost and effectiveness.

In order to test the compounds of the present invention, various fats, fatty acids and paraffin wax were subjected to the Modified Swift Stability Test (active oxygen method). This method is described in Oil and Soap, 22, 101 (1945), audit: J. Am. Oil Chem. Soc., 25, 42 (1948). In this test, air is bubbled continuously through a 20 ml. sample which may or may not contain an antioxidant, and maintained at 97.7 C. The air rate is about ml./min. Periodically, small portions of the sample are removed and the peroxide number of the portion determined. The magnitude of the peroxide number is a recognized index of the extent to which undesirable oxidation of the sample has occurred and, therefore, inversely reflects the effectiveness of the antioxidant which may be present in the sample. A peroxide number of about 25 to 35 milliequivalents per kilogram (meq./kg.) is the maximum tolerable for most uses of fatty acids; discoloration and/or rancidity usually become apparent at about this point. Accordingly, it is obvious that different antioxidants may be easily compared on the bases of the induction periods of the samples (or time to first appearance of peroxides), and time for the sample to attain a peroxide number in the range of 2535 meq./kg. it is also obvious that the longer the induction period and/ or the time to maximum tolerable peroxide number, the more effective and valuable the antioxidant. It is obvious that the highest value is attached to an antioxidant which can prevent appearance of any peroxides and rancidity for any desired length of time.

The specific rhodanine-type compounds tested were as follows:

Rhodanine 3-p-hydroxyphenylrhodanine S-methylrhodanine 3-n-butylrhodanine S-furfurylidenerhodanine 3-methyl-5-ethylrhodanine 2,soo,491

The data obtained are as follows: 5. The process of stabilizing a member selected from Cone, induction Time to Reach Peroxide Fatty Material Antioxidant Percent Pgiod, No. of 35 meq.[kg., hrs.

No Tenox BHA I 0.025 16 40 g-p-hldrloxly-gheiiigl rhodanine 0 18 -me y -r 0 an e 0 28 Steam: Acid 1 3-n-butyl-rhodanine 0.026 0 56 5-lurlurylidenerhodanine 0. 025 20 80 3-methyl-{rethylrhodanina 0. 025 42 B0 Rhodanine 0. 025 336 meq.!kg., hrs.)

Proprietary T 42 90 Lily Stearie Acid B'hod'mme r 0. 025 100 (20 meq./kg., min.)

None 0 45 0191 Acid {Rhodanine 0. 02s 0 105 Time to reach eroxide No. of 10 meq. g., hrs.

3-n-butyl rhodanine 3 Lard Oil 3-methyl5ethy1rhodanlne 8 None 4% Tndnr-flnn Alter 65 days Period, Days Color Acid N 0.

None 12 Orange 109. 6 Paraffin wax Rhodanine Pale yellow.- 38. 0 -do 62 White 2.2

HA, butylated hydroxyanisole, Tennessee-Eastman Corporation.

The data show that rhodanine is an exceptionally good 35 antioxidant, particularly for saturated fatty acids. No significant amount of peroxides or rancidity could be detected in any of the samples containing 0.025% rhodanine, regardless of the length of time the tests were run. Lower concentrations are somewhat less effective, although still useful, as shown by comparison with the data for Tenox BHA, and for Lily Stearic Acid without additional antioxidant. Rhodanine is less effective at 0.025% as an antioxidant for unsaturated fatty acids (e. g., oleic acid), than for saturated fatty acids.

Fatty acids which can be stabilized in accordance with the present invention include both saturated acids having the formula CnHsn+1COOH, and unsaturated fatty acids having the formula CnH2"- 1COOH, in both cases n being a number from 6 to 22. Typical fatty acids which may be stabilized include but are not limited to: caprylic, capric, lauric, palmitic, oleic, stearic, capronic, myristic, arachidic, petroselinic, vaccenic, eleostearic, licamic, parinaric, gadoleic, arachiodonic and cetoleic acids.

I claim:

1. The process of stabilizing a member selected from the group consisting of fatty acids, fats, and paraffin wax comprising adding thereto a rhodanine of the formula wherein R1 and R2 are selected from the group consisting of hydrogen atoms, alky'l, aryl, alkaryl, aralkyl and heterocyclic organic radicals.

2. The process of stabilizing a member selected from the group consisting of fatty acids, fats, and paraifin wax comprising adding thereto rhodanine.

3. The process of stabalizing a member selected from the group consisting of fatty acids, fats, and paraffin wax comprising adding thereto 3-o-hydroxyphenyl rhodanine.

4. The process of stabilizing a member selected from the group consisting of fatty acids, fats, and paraffin wax comprising adding thereto S-methyl rhodanine.

the group consisting of fatty acids, fats, and paraffin wax comprising adding thereto 3-n-butyl rhodanine.

6. The process of stabilizing a member selected from the group consisting of fatty acids, fats and paraflin wax comprising adding thereto 3-methyl-5-ethyl rhodanine.

7. The process of stabilizing commercial stearic acid comprising adding thereto about 0.025% by weight of rhodanine.

8. The process of stabilizing a mixture containing stearic and palmitic acids comprising adding thereto about 0.025% rhodanine.

9. The process of stabilizing paraffin wax comprising adding thereto a small amount of rhodanine.

10. As a new composition of matter, a mixture of a member selected from the group consisting of fatty acids, fats and paraffin wax and a rhodanine of the formula wherein R1 and R2 are selected from the group consisting of hydrogen atoms, alkyl, aryl, alkaryl, aralkyl and heterocyclic organic radicals.

11. As a new composition of matter, a member selected from the group consisting of fatty acids, fats, and paraffin wax and rhodanine.

12. As a new composition of matter, a mixture of a member selected from the group consisting of fatty acids, fats, and paraffin wax and 3-o-hydroxyphenyl rhodanine.

13. As a new composition of matter, a mixture of a member selected from the group consisting of fatty acids, fats, and parafiin wax and S-methyl rhodanine.

14. As a new composition of matter, a mixture of a member selected from the group consisting of fatty acids, fats, and paraffin wax and 3-n-butylrhodanine.

15. As a new composition of matter, a mixture of a member selected from the group consisting of fatty acids, fats, and parafiln wax and 3-methyl-5-ethyl rhodam'ne.

16. As a new composition of matter, commercial 18. As a new composition of matter, parafiin wax containing a small amount of rhodanine.

stearic acid containing about 0.025% by weight rhodanine.

1 danine.

17. As a new composition of matter, a mixture of steam: and palm'tic acids containing about 0.025% 1110- References Cited in the file of this patent UNITED STATES PATENTS 2,469,378

Flatt May 10, 1949 

1. THE PROCESS OF STABILIZING A MEMBER SELECTED FROM THE GROUP CONSISTING OF FATTY ACIDS, FATS, AND PARAFFIN WAX COMPRISING ADDING THERETO A RHODANICE OF A FORMULA 